1. Field of the Invention
The present invention relates to a cooling device for cooling an electronic component such as a semiconductor module, and a power conversion device or converter equipped with the cooling device.
2. Description of the Related Art
Electric power conversion devices, such as inverters, converters and so on, that are equipped with a plurality of semiconductor modules with semiconductors incorporated therein and a cooling device for cooling the semiconductor modules are known heretofore.
One example of such known power conversion devices is disclosed in Japanese Patent Laid-open Publication (JP-A) No. 2001-320005 (corresponding to U.S. Pat. No. 7,248,478). The disclosed power conversion device includes a pair of cooling tubes disposed on both sides of a semiconductor module. The cooling tubes are urged toward each other by means of presser plates and a spring member so that the cooling tubes come closely in contact with the semiconductor module.
However, due to the use of the presser plates and the spring member, the spacing between a stacked or laminated array of semiconductor modules is relatively large, making it difficult to downsize the power conversion device.
Japanese Patent Laid-open Publication (JP-A) No. 2005-191082 (corresponding to U.S. Patent Application Publication No. 2007/0044952) shows another example of the known power conversion devices, wherein semiconductor modules and cooling tubes are disposed alternately so as to reduce the spacing between the semiconductor modules stacked or laminated together with the cooling devices disposed therebetween. A laminated assembly as a whole is compressed in a laminated direction (thickness direction of semiconductor modules) so that the semiconductor modules and the cooling tubes closely contact each other.
With this arrangement, since the laminated assembly, which is composed of a plurality of semiconductor modules and a plurality of cooling tubes, is compressed by only one pressure means, the compressive force or pressure acting between the semiconductor modules and the cooling devices is uniform throughout the laminated assembly. It may occur, however, that the plural semiconductor modules are not uniform in heat value and hence require a different cooling efficiency provided for each of the semiconductor module. In this instance, the foregoing arrangement is not convenient because the pressure acting between the semiconductor modules and the cooling tubes is uniform throughout the assembly. If the pressure is set to be suitable for a semiconductor module having a maximum heat value, an excessively large pressure will be applied to the entire laminated assembly.
The power conversion device shown in JP 2005-191082A is arranged to change the flow rate of a cooling medium flowing through the cooling tubes in accordance with the heat values of the associated semiconductor modules. This arrangement, however, lacks versatility because of the design requirements in which a thermal balance must be provided for a plurality of different circuit control patterns in view of the thermal interference between the adjacent semiconductor modules and the difference in flow distribution of the cooling medium.
Still another example of the known power conversion devices is disclosed in Japanese Patent Laid-open Publication (JP-A) No. 2006-313848. The disclosed power conversion device has an arrangement to supply a high-pressure cooling medium or coolant through a cooling tube so that the cooling tube is expanded and comes closely in contact with electronic components. This arrangement is, however, difficult to realize because the entire coolant circulation path requires a high pressure-proof design. Furthermore, since the pressure applied from the cooling tube to the respective electronic components is uniform throughout the electronic component and cooling tube assembly, the same problem as the one discussed above with respect to JP 2005-191082A will occur.